Zigzag sewing mechanism of double-thread sewing machine



H. SUDO Nov. 1, 1955 ZIGZAG SEWING MECHANISM OF DOUBLE-THREAD SEWING MACHINE Filed April 2, 1951 2 Sheets-Sheet l FIG.

FIG. Ill

H. SUDO Nov. 1, 1955 ZIGZAG SEWING MECHANISM OF DOUBLE-THREAD SEWING MACHINE Filed April 2, 1951 2 Sheets-Sheet 2 FIG. IV

United States Patent ZIGZAG SEWING MECHANISM OF DOUBLE- THREAD SEWING MACHINE Hidenori Sudo, Osaka, Japan Application April 2, 1951, Serial No. 218,789 Claims priority, application Japan April 5, 1950 2 Claims. (Cl. 11215) This invention relates to a device whereby the zigzag sewing mechanism in a lock stitch machine (double yarn sewing machine) is divided into the periodic oscillating section and the zigzag amount changing section. In the periodic oscillating section the starting and finishing time of the zigzag motion is made constant in any seams, and in the zigzag amount changing section it is made possible, by means of differential gear mechanism, to have a joint use of hand operation and knee operation, and especially to perform a complicated embroidery sewing by the knee operation using both hands at the same time. The lock stitch machine here referred to is of the general type shown in my copending application Ser. No. 218,788, filed of even date herewith, now Patent No. 2,690,723, granted October 5, 1954.

Fig. I is a front view of the principal parts of the mechanism of this invention. Fig. II is a plan view of the mechanism of Fig. I, taken from the bottom, and Fig. III is a view in elevation from the right side of Fig. I, with the knee lever added. Fig. IV is an illustration showing the function of this mechanism as compared with that of the ordinary well-known type.

This mechanism performs the zigzag sewing in a lock stitch machine, and comprises an improvement upon the ordinary well-known type in that it removes the defect due to error from a disagreement in time of the start and finish of the forked connecting rod, or in other words, the defect of the possibility of the shifting of the position of zigzag before the needle comes completely out of the cloth or just when it is about to come through.

Below is given the explanation of an embodiment of the present invention.

The triangular cam 4 which is rotated from the main shaft 1 through the speed reduction gears 2, 3 with a speed ratio of 2 to 1 is fitted in with the forked connecting rod 27 which is supported by the shaft 30 separately from the arcuately grooved link 28. The latter is pivoted by the shaft 6 through the arm lever 8 unitary with the sleeve or cylinder 42, of the zigzag shifting lever 7. This cylinder 421 is pivotally supported on the basic shaft 9 as is the cylinder 42 of the zigzag amount change lever 40 hereinafter referred to. When the lever 7 is shifted the arm lever 8 turns, moving the arcuately grooved link 28 and the connecting link 29. The arcuately grooved link 28 and the lower part of the forked connecting rod 27 are connected with each other by means of the connecting link 29. There is a connecting rod 11, which is connected with the arcuately grooved link 28 by a slider 13 fitted within the groove. The other end of the rod 11 is connected with the needlebar through the end of the arm plate 17 which is set upon the oscillating rock shaft 35 of the shuttle. One end of a coupling 31 which is parallel to the connecting rod 11 is connected with the center of the connecting rod 11 by means of the connecting piece 24. A shaft 32 inserted in the said coupling 31 and the small bevel gear 33 fitted in with it are geared to each other in such a manner that they are closed in between the upper gear 37 and the lower bevel gear 36 which are fitted to the support shaft 34 and are confronted with each other. At the same time a small arm piece 38 which is provided at the end of the extension of the upper gear 37 and an arm piece 39 protruding from the basic cylinder part 42 of a zigzag amount change lever 40 are connected with each other by means of a connecting plate 41, thereby increasing the swing of the small arm piece 38. The other bevel gear 36 is fastened tight to the support shaft 34, and the knee-operated lever 43 is provided on the said shaft (see Fig. IH).

The motion for the needle-bar and the shuttle is made to reach from the shaft 14 at the arm plate 17 of the oscillating rock shaft 35 to the head of the needle-bar by means of the connecting piece 15 and the connecting rod 16. At the same time from the arm at the lower portion of the oscillating rock shaft 35 which has exactly the same motion as the arm plate 17, the movements go to the oscillating connecting piece of the shuttle, also by means of the connecting rod (drawing omitted).

Referring now to the conventional well-known type of zigzag sewing mechanism, if the position-shifting lever 7 (see Fig. II) is shifted to the extreme right, the parts assume the position shown in part A of Fig. IV. The connecting shaft 6 pivoted with the arcuately grooved link formed together with the forked connecting rod, is positioned on the radius 6r of a circle with the basic shaft 9 of the position shifting lever as the center, and if the eccentric radius of the triangular cam 4 is a, the eccentric circle 26 has the radius a from the center of the shaft 25. If the distance 6m, 6r on which the connecting shaft 6 has travelled to the right from the time when it was at middle position is made equal to the eccentric radius a, the tangent line 6r, d, which is drawn from 6r to the eccentric circle, is parallel to the line the basic shaft 9 makes with the cam shaft 25. At right angles to this line is the line X, X. side b, b of the triangular cam rotates on the said line X, X and is positioned accordingly, it is the time of the stoppage of the swinging of the forked connecting rod.

Next, when the connecting shaft 6 is moved to the extreme left and positioned at 6L as shown in Fig. IV, B, the stoppage of the swinging does not begin even if the operating side b, b of the triangular cam 4 comes rotating to the line X, X. The swinging begins to stop only, when the line e, e which is at right angles to the tangent line 6L, d which is drawn from 6L to the eccentric circle 26 is reached. Consequently there is an error in the amount of the angle 0 which the line X, X makes with the line e, e.

That is:

2a distance of 6m 25 Furthermore, since the main shaft rotates twice to every once for the cam, there occurs a deviation of 4a distance of 6m 25 in the angular motion of the main shaft. This is an error due to the design of the machine. In other Words, it is an error when the shifting of the zigzag is started before the needle comes completely out of the cloth or when it is about to come through.

The present invention has removed the above mentioned defect. In this invention the forked connecting rod 27 and the arcuately grooved link 28 are divided, and connected with the connecting piece between them. Since the center 30 of the swinging of the forked connecting rod 27 is fixed, the time of stoppage and start fixes the condition of the shaft 6.

Describing the above mentioned improvement according to Fig. IV, C, is as follows:

When the operating If the line which is at right angles to the common inscribed line b, b of the eccentric circle 26 and the circle having as radius the level distance between the shaft 30 and the cam shaft 25 is g, g, the line g, g is a fixed straight line. When the triangular cam 4 rotates and its acting side b, b reaches this line g, g, the stoppage of the swinging motion begins and its time is always the same. Even if the shaft 6 comes at either position, right or left, the forked connecting rod 27 is not affected, as there is the connecting rod 29.

This invention proposes to put into practice the motion mechanism demonstrated by the explanation given above, and at the same time perform the operation of changing the amount of zigzag by a joint use of hand operation and knee operation. Referring to Fig. III, if the zigzag amount changing lever 40 is moved to the right, the basic cylinder part 42 is turned, and its arm piece 39 causes the connecting plate 41 to move. The arm piece 38, which has a smaller radius than the radius of the arm piece 39 turns the upper bevel gear, thereby rotating the small bevel gear 33. But the lower bevel gear 36 does not rotate, and consequently does not transmit rotation, and the shaft 32 works in the direction of the arrow with the shaft 34 as the center (see Fig. I). The coupling 31 is shifted downward and the connecting rod 11 is rotated by the connecting piece 24, thereby moving the slider 13 away from the shaft 6, thus increasing the amount of swinging of the arcuately grooved link 28. In this manner the object of changing the amount of zigzag is achieved by hand operation.

If the shaft 34 is rotated by means of the knee operated lever 43, without using the hand operated zigzag amount changing lever 40, the small bevel gear 33 is rotated through the lower bevel gear 36 in a manner similar to the above, and since the motion is not transmitted to the upper bevel gear 37, the shaft 32 is turned with the shaft 34 as the center, and thus the object of changing the amount of zigzag by knee operation is achieved.

Pin 4-1 is provided to limit the motion of the shaft 32, so that it does not rotate more than is necessary.

Consequently, this device of changing the zigzag amount by a joint use of hand operation and knee operation can be used to great advantage particularly for embroidery.

I claim:

1. In a double-thread sewing machine having a needle bar, a shuttle and a zigzag sewing mechanism, a main shaft, speed reduction gears driven by the main shaft, a triangular cam driven by the gears, a forked connecting rod fitted in with the cam, a zigzag shifting lever an a zigzag amount change lever, a common basic shaft on which said zigzag shifting and amount change levers are pivotally mounted, an arm lever unitary with the zigzag shifting lever, and an arcuately grooved link pivoted from the arm lever, a slider in the arcuately grooved link, a shaft supporting the forked rod separately from the arcuately grooved link, a link connecting the arcuately grooved link and the lower end of the forked rod, a second connecting rod engaged at one end to the slider and operatively linked at the other end with the needle bar and the shuttle, a connecting piece connected to the middle of the second connecting rod, a coupling parallel to the second connecting rod and joined to the said connecting piece, a coupling shaft inserted in said coupling, a small bevel gear on said coupling shaft, a support shaft at right angles to the coupling shaft, upper and lower bevel gears on the support shaft meshing with the small gear, one being tight on the support shaft and the other loose, and a small arm piece associated with the loose bevel gear on the support shaft, in combination with a second longer arm piece protruding from part of the zigzag amount change lever and a plate connecting said two arm pieces, whereby the swing of the small arm piece can be increased by moving the amount change lever.

2. In a double-thread sewing machine according to claim 1, the provision of a knee-operated lever on the tight bevel gear on the support shaft with which the arm pieces are not associated; whereby motion of the knee lever turns the support shaft causing a change in the amount of zigzag by knee operation and zigzag embroidery sewing can be controlled jointly by hand and knee operation.

Italy Sept. 17, 1938 Germany Aug. 9, 1940 

